Fiber optic cables may be terminated in two ways—with connectors that can mate two fibers to create a temporary joint and/or connect the fiber to a piece of network equipment or with splices which create a permanent joint between the two fibers. Two basic fiber optic cable designs include loose tube cables and tight buffered cables. Loose tube cables can be designed to endure outside environmental conditions. In a loose tube cable, one or more optical fibers are loosely positioned within a buffer tube contained within an outer jacket of the cable. The buffer tube can be filled with gel to prevent water from migrating along a length of the buffer tube.
Over the years, numerous connector types have been developed. Although the mechanical design varies significantly among different fiber optic connector types, most fiber optic connectors include a fiber ferrule made of ceramic, such as zirconia, or metal, such as stainless steel and a ferrule holder, commonly known as a hub, retaining the ferrule. Other ferrules (e.g., multi-fiber ferrules) can be made of other types of materials such as thermoset materials (e.g., epoxy) or thermoplastic materials (e.g., polyphenylene sulfide (pps)). In the case of single fiber ferrules, a high precision hole is formed (e.g., drilled) in the center of the ferrule, and a stripped bare fiber (the glass core and glass cladding with the coating removed) is inserted through and usually bonded by an adhesive such as epoxy.
Adhesive such as epoxy is used to secure/pot an optical fiber within the ferrule and ferrule hub of a fiber optic connector. Voids or air pockets within the epoxy filling the ferrule hub can leave part of the optical fiber unsupported or unevenly supported thereby increasing the likelihood of optical fiber breakage.
One way of terminating a loose tube fiber optic cable with a fiber optic connector is to inject epoxy into the ferrule and then push the fiber into the ferrule. Alternatively, epoxy is applied to the fiber before the fiber is pushed into the ferrule. If the end of the loose tube spaced from the connector is sealed, the expansion of air inside the tube when curing the epoxy at high temperatures will push air out the end of the loose tube adjacent the connector there introducing bubbles (i.e., voids or air pockets) within the epoxy filling the ferrule hub. Alternatively, if the far end of the loose tube is open, capillary action will draw epoxy into the loose tube from the ferrule hub and leave an insufficient amount of epoxy in the ferrule hub and/or the ferrule.
Attempts have been made to reduce the likelihood of introducing air pockets in the epoxy potting a fiber of a fiber optic connector during assembly of the fiber optic connector. Example attempts are disclosed in U.S. Pat. Nos. 5,381,497; 6,936,122 and 7,708,469, the disclosures of which are hereby incorporated by reference in their entireties. Despite these attempts, improvements are still needed.